UCLA Type Implant Crown: Indications?

Dear Student: The UCLA abutment was designed to fix implant angulation problems and in some cases depth poblems (too much or too little). Since it was fully castable you could do pretty much everything with it,a direct crown or a personalized abutment for a cemented crown or bridge, a dolder type bar, I have even seen ball attachemnts made to an angle with this abutments. The problem with fully castable UCLAs is the implant abutment precision adjustement gap that is .... not good.(to say the least) a casted abutmet cant compete with a machined abutment. That is why some "clever guy" invented the overcasted UCLA that has a metal base (Ti or CrCo or AU) with a plastc sleeve and you overcast so you get the flexibility of doing almost everythng with almost the precision of machined abutment. Not my personal choice but have used the later with great success. I hope this helped

To add to the last comment, the trouble with the over cast is that it is technique sensitive and expensive. One mis-cast and you double your cost. One of the UCLA over cast abutments can run $190 or more. The real answer comes in the foarm of Custom Computer Aided Design-CAD. Custom CAD abutments have a machined implant interface, provide for angle correction, improved esthetics, parallalism, ideal emerfence profile, proper cervical tooth size and are easy and predictable to fabricate. All the advantages of the UCLA with none of the disadvantages. Plus they can be milled from titanium or zirconia for the esthetic zone.

To answer your specific question, while it would be technically possible to make a UCLA crown and torque it to the implant fixture, I can not think of an indication to do it that way. Maybe if your philosophy is 100% screw retained, but you are asking for other issues besides such as screw access location and maintenance. We can go on and on but with custom CAD abutment and a cemented crown I have had very very few problems in 15+ years and it is very predictable.

I believe there are very few indications for the UCLA style of abutment. The prime reason being that the gingival interface requires a Titanium or Zirconium abutment to get good hemi-desmasomal attachment of the gingiva to the abutment, thereby providing a tight gingival seal. This does NOT occur with a gold or porcelain interface. It is possible to cast a UCLA abutment in Titanium, but the technique is difficult, expensive and the end result is usually not as satisfactory as a modified stock Titanium abutment. A Zirconia interface appears to be satisfactory, but the strength of the Zirconia abutment is considerably less than a Titanium abutment, and the Zirconia abutment should be reserved for selected esthetic cases only.

As per the 'KISS' principle (Keep It Simple...)from the clinical point of view subject to suitable angulations UCLA castable abutments certainly have a lot going for them. However, they are not terribly suitable for large multi unit internal connection cases; not that one has ANY errors at all in ones impressions of course (!), but any miniscule distortion will effectively be magnified by the length of the abutment, preventing passive fit

One use for a UCLA style one piece crown/abutment is in an area where inter-occlusal space is limited. This could be due to tooth position or an implant not placed deep enough. Sometimes it is impossible to get subgingival emergence, a 5mm tall wall on the abutment, and room for the restoration. Therefore a screw-retained crown/abutment can fix a tough restorative situation and achieve a positive outcome.

From my point of view, the real mean of the screw retained crown/abutment UCLA is: Universal Clearance Limited Abutment. Elie Warde DDS